scholarly journals Lipoproteins Are Responsible for the Pro-Inflammatory Property of Staphylococcus aureus Extracellular Vesicles

2021 ◽  
Vol 22 (13) ◽  
pp. 7099
Author(s):  
Pradeep Kumar Kopparapu ◽  
Meghshree Deshmukh ◽  
Zhicheng Hu ◽  
Majd Mohammad ◽  
Marco Maugeri ◽  
...  
Keyword(s):  
Extracellular Vesicles ◽  
Inflammatory Responses ◽  
Surface Proteins ◽  
Host Cells ◽  
Immune Stimulation ◽  
Domains Of Life ◽  
Major Surface ◽  
Staphylococcal Aureus

Staphylococcal aureus (S. aureus), a Gram-positive bacteria, is known to cause various infections. Extracellular vesicles (EVs) are a heterogeneous array of membranous structures secreted by cells from all three domains of life, i.e., eukaryotes, bacteria, and archaea. Bacterial EVs are implied to be involved in both bacteria–bacteria and bacteria–host interactions during infections. It is still unclear how S. aureus EVs interact with host cells and induce inflammatory responses. In this study, EVs were isolated from S. aureus and mutant strains deficient in either prelipoprotein lipidation (Δlgt) or major surface proteins (ΔsrtAB). Their immunostimulatory capacities were assessed both in vitro and in vivo. We found that S. aureus EVs induced pro-inflammatory responses both in vitro and in vivo. However, this activity was dependent on lipidated lipoproteins (Lpp), since EVs isolated from the Δlgt showed no stimulation. On the other hand, EVs isolated from the ΔsrtAB mutant showed full immune stimulation, indicating the cell wall anchoring of surface proteins did not play a role in immune stimulation. The immune stimulation of S. aureus EVs was mediated mainly by monocytes/macrophages and was TLR2 dependent. In this study, we demonstrated that not only free Lpp but also EV-imbedded Lpp had high pro-inflammatory activity.

scholarly journals Leishmania mexicana Mutants Lacking Glycosylphosphatidylinositol (GPI):Protein Transamidase Provide Insights into the Biosynthesis and Functions of GPI-anchored Proteins

2000 ◽  
Vol 11 (4) ◽  
pp. 1183-1195 ◽  
Author(s):  
James D. Hilley ◽  
Jody L. Zawadzki ◽  
Malcolm J. McConville ◽  
Graham H. Coombs ◽  
Jeremy C. Mottram
Keyword(s):  
Normal Growth ◽  
Surface Proteins ◽  
Host Cells ◽  
Mammalian Host ◽  
Putative Protein ◽  
Major Class ◽  
Major Surface Proteins ◽  
Major Surface

The major surface proteins of the parasitic protozoonLeishmania mexicana are anchored to the plasma membrane by glycosylphosphatidylinositol (GPI) anchors. We have cloned the L. mexicana GPI8 gene that encodes the catalytic component of the GPI:protein transamidase complex that adds GPI anchors to nascent cell surface proteins in the endoplasmic reticulum. Mutants lacking GPI8 (ΔGPI8) do not express detectable levels of GPI-anchored proteins and accumulate two putative protein–anchor precursors. However, the synthesis and cellular levels of other non–protein-linked GPIs, including lipophosphoglycan and a major class of free GPIs, are not affected in the ΔGPI8 mutant. Significantly, the ΔGPI8 mutant displays normal growth in liquid culture, is capable of differentiating into replicating amastigotes within macrophages in vitro, and is infective to mice. These data suggest that GPI-anchored surface proteins are not essential to L. mexicana for its entry into and survival within mammalian host cells in vitro or in vivo and provide further support for the notion that free GPIs are essential for parasite growth.

scholarly journals Therapeutic Effects of Hypoxic and Pro-Inflammatory Priming of Mesenchymal Stem Cell-Derived Extracellular Vesicles in Inflammatory Arthritis

2021 ◽  
Vol 23 (1) ◽  
pp. 126
Author(s):  
Alasdair G. Kay ◽  
Kane Treadwell ◽  
Paul Roach ◽  
Rebecca Morgan ◽  
Rhys Lodge ◽  
...  
Keyword(s):  
T Cell ◽  
Extracellular Vesicles ◽  
Inflammatory Responses ◽  
Therapeutic Potential ◽  
Histopathological Analysis ◽  
Therapeutic Effects ◽  
Synovial Joint ◽  
Paracrine Signalling

Mesenchymal stem cells (MSCs) immunomodulate inflammatory responses through paracrine signalling, including via secretion of extracellular vesicles (EVs) in the cell secretome. We evaluated the therapeutic potential of MSCs-derived small EVs in an antigen-induced model of arthritis (AIA). EVs isolated from MSCs cultured normoxically (21% O2, 5% CO2), hypoxically (2% O2, 5% CO2) or with a pro-inflammatory cytokine cocktail were applied into the AIA model. Disease pathology was assessed post-arthritis induction through swelling and histopathological analysis of synovial joint structure. Activated CD4+ T cells from healthy mice were cultured with EVs or MSCs to assess deactivation capabilities prior to application of standard EVs in vivo to assess T cell polarisation within the immune response to AIA. All EVs treatments reduced knee-joint swelling whilst only normoxic and pro-inflammatory primed EVs improved histopathological outcomes. In vitro culture with EVs did not achieve T cell deactivation. Polarisation towards CD4+ helper cells expressing IL17a (Th17) was reduced when normoxic and hypoxic EV treatments were applied in vitro. Normoxic EVs applied into the AIA model reduced Th17 polarisation and improved Regulatory T cell (Treg):Th17 homeostatic balance. Normoxic EVs present the optimal strategy for broad therapeutic benefit. EVs present an effective novel technology with the potential for cell-free therapeutic translation.

scholarly journals Influenza’s Newest Trick

mBio ◽  
2019 ◽  
Vol 10 (6) ◽  
Author(s):  
Jeffery K. Taubenberger
Keyword(s):  
Influenza A ◽  
Rna Virus ◽  
Surface Proteins ◽  
Host Cells ◽  
Influenza A Viruses ◽  
Protease Activation ◽  
Major Surface Proteins ◽  
Major Surface ◽  
Cleavage Motif

ABSTRACT Influenza A viruses are important pathogens for humans and for many birds and mammals. Hemagglutinin and neuraminidase are the major surface proteins of this enveloped RNA virus. Hemagglutinin requires proteolytic cleavage for activation, but because the viral genome does not encode its own protease, an exogenous serine protease must be provided by host cells. A novel, neuraminidase-dependent mechanism for hemagglutinin activation was described, in which a thrombin-like protease allows an influenza A/H7N6 virus, isolated from a mallard duck, to replicate systemically and induce enhanced disease in avian and mammalian model animals and to replicate in vitro in the absence of trypsin. Thrombin-like protease activation required the N6 neuraminidase, but also required the presence of a thrombin-like cleavage motif in the H7 hemagglutinin. This novel example of neuraminidase-dependent hemagglutinin activation demonstrates the extraordinary evolutionary flexibility of influenza A viruses and is a fascinating example of epistasis between the hemagglutinin and neuraminidase genes.

scholarly journals Neutrophil-Derived Extracellular Vesicles Activate Platelets after Pneumolysin Exposure

Cells ◽  
2021 ◽  
Vol 10 (12) ◽  
pp. 3581
Author(s):  
Eleftheria Letsiou ◽  
Luiz Gustavo Teixeira Alves ◽  
Matthias Felten ◽  
Timothy J. Mitchell ◽  
Holger C. Müller-Redetzky ◽  
...  
Keyword(s):  
Extracellular Vesicles ◽  
Platelet Activation ◽  
Annexin V ◽  
Surface Proteins ◽  
Cooperative Interaction ◽  
Proteinase K ◽  
Cell Surface Expression ◽  
Pneumococcal Infections

Pneumolysin (PLY) is a pore-forming toxin of Streptococcus pneumoniae that contributes substantially to the inflammatory processes underlying pneumococcal pneumonia and lung injury. Host responses against S. pneumoniae are regulated in part by neutrophils and platelets, both individually and in cooperative interaction. Previous studies have shown that PLY can target both neutrophils and platelets, however, the mechanisms by which PLY directly affects these cells and alters their interactions are not completely understood. In this study, we characterize the effects of PLY on neutrophils and platelets and explore the mechanisms by which PLY may induce neutrophil–platelet interactions. In vitro studies demonstrated that PLY causes the formation of neutrophil extracellular traps (NETs) and the release of extracellular vesicles (EVs) from both human and murine neutrophils. In vivo, neutrophil EV (nEV) levels were increased in mice infected with S. pneumoniae. In platelets, treatment with PLY induced the cell surface expression of P-selectin (CD62P) and binding to annexin V and caused a significant release of platelet EVs (pl-EVs). Moreover, PLY-induced nEVs but not NETs promoted platelet activation. The pretreatment of nEVs with proteinase K inhibited platelet activation, indicating that the surface proteins of nEVs play a role in this process. Our findings demonstrate that PLY activates neutrophils and platelets to release EVs and support an important role for neutrophil EVs in modulating platelet functions in pneumococcal infections.

scholarly journals Monoclonal antibody with hemagglutination, immobilization, and neutralization activities defines an immunodominant, 47,000 mol wt, surface-exposed immunogen of Treponema pallidum (Nichols).

1984 ◽  
Vol 160 (5) ◽  
pp. 1404-1420 ◽  
Author(s):  
S A Jones ◽  
K S Marchitto ◽  
J N Miller ◽  
M V Norgard
Keyword(s):  
Treponema Pallidum ◽  
Immune Serum ◽  
Host Cells ◽  
Rabbit Serum ◽  
Functional Activities ◽  
Molecular Weights ◽  
Rabbit Igg ◽  
Major Surface

Radioimmunoprecipitation (RIP) analyses performed on 125I-surface-labeled Treponema pallidum cells using various immune sera revealed the presence of six major surface antigens (immunogens) with apparent molecular weights of 47 K, 36 K, 34 K, 32 K, 29 K, and 13 K. Among these, the 47 K surface antigen was most abundant. Radioimmunoprecipitation assays using 125I-labeled T. phagedenis biotype Reiter or immunoblot analyses using the same strain, failed to reveal the presence of the 47 K mol wt antigen in the representative nonpathogenic treponeme. Preabsorption of anti-T. pallidum immune rabbit serum (IRS) with the Reiter organism did not remove anti-T. pallidum antibodies from immune serum that reacted with the 47 K mol wt immunogen or other immunogens of T. pallidum present in the characteristic antigenic profile. Monoclonal antibodies (mAb) directed specifically against the 47 K mol wt immunogen of T. pallidum also failed to react with an analogous 47 K mol wt component in Treponema phagedenis biotype Reiter, further suggesting the unique presence of this antigen in pathogenic treponemes. The presence of the 47 K mol wt surface immunogen in pathogenic treponemes other than T. pallidum subspecies pallidum was also observed (43). Anti-47 K immunogen mAb was nonreactive against rabbit IgG or IgM. mAb directed specifically against the 47 K mol wt immunogen of T. pallidum was examined for strategic functional activities. It was found to be reactive in the microhemagglutination assay for T. pallidum antibodies, the T. pallidum immobilization test, and was found to be capable of significant blockage of attachment of virulent T. pallidum to host cells in tissue culture. Additional significant biological activity for the anti-47 K mol wt immunogen mAb was revealed through results of the in vitro-in vivo neutralization test of Bishop and Miller, in which a 99% or 100% neutralizing activity was demonstrated. The combined data of this study suggest that the 47 K mol wt immunogen of T. pallidum represents an abundant, immunodominant, surface-exposed immunogen possessing potential biological importance in the pathogenesis and immunology of T. pallidum infection. These studies serve to establish the first functionally defined immunogen for T. pallidum, which may represent the major immunogen of the organism.

scholarly journals The Triad Hsp60-miRNAs-Extracellular Vesicles in Brain Tumors: Assessing Its Components for Understanding Tumorigenesis and Monitoring Patients

2021 ◽  
Vol 11 (6) ◽  
pp. 2867
Author(s):  
Francesca Graziano ◽  
Domenico Gerardo Iacopino ◽  
Giacomo Cammarata ◽  
Gianluca Scalia ◽  
Claudia Campanella ◽  
...  
Keyword(s):  
Brain Tumors ◽  
Extracellular Vesicles ◽  
Current Knowledge ◽  
Disease Status ◽  
Experimental Models ◽  
Host Cells ◽  
Target Cells ◽  
Original Cell

Brain tumors have a poor prognosis and progress must be made for developing efficacious treatments, but for this to occur their biology and interaction with the host must be elucidated beyond current knowledge. What has been learned from other tumors may be applied to study brain tumors, for example, the role of Hsp60, miRNAs, and extracellular vesicles (EVs) in the mechanisms of cell proliferation and dissemination, and resistance to immune attack and anticancer drugs. It has been established that Hsp60 increases in cancer cells, in which it occurs not only in the mitochondria but also in the cytosol and plasma-cell membrane and it is released in EVs into the extracellular space and in circulation. There is evidence suggesting that these EVs interact with cells near and far from their original cell and that this interaction has an impact on the functions of the target cell. It is assumed that this crosstalk between cancer and host cells favors carcinogenesis in various ways. We, therefore, propose to study the triad Hsp60-related miRNAs-EVs in brain tumors and have standardized methods for the purpose. These revealed that EVs with Hsp60 and related miRNAs increase in patients’ blood in a manner that reflects disease status. The means are now available to monitor brain tumor patients by measuring the triad and to dissect its effects on target cells in vitro, and in experimental models in vivo.

scholarly journals Absence of Platelet Endothelial Cell Adhesion Molecule 1, PECAM-1/CD31,In VivoIncreases Resistance to Salmonella enterica Serovar Typhimurium in Mice

2013 ◽  
Vol 81 (6) ◽  
pp. 1952-1963 ◽  
Author(s):  
Michael D. Lovelace ◽  
May Lin Yap ◽  
Jana Yip ◽  
William Muller ◽  
Odilia Wijburg ◽  
...  
Keyword(s):  
Salmonella Enterica ◽  
Inflammatory Responses ◽  
Bacterial Load ◽  
Host Cells ◽  
Dependent Manner ◽  
Wild Type ◽  
Mesenteric Lymph Nodes ◽  
Serovar Typhimurium

ABSTRACTPECAM-1/CD31 is known to regulate inflammatory responses and exhibit pro- and anti-inflammatory functions. This study was designed to determine the functional role of PECAM-1 in susceptibility to murine primaryin vivoinfection withSalmonella entericaserovar Typhimurium and inin vitroinflammatory responses of peritoneal macrophages. Lectin profiling showed that cellular PECAM-1 and recombinant human PECAM-1-Ig chimera contain high levels of mannose sugars andN-acetylglucosamine. Consistent with this carbohydrate pattern, both recombinant human and murine PECAM-1-Ig chimeras were shown to bindS. Typhimurium in a dose-dependent mannerin vitro. Using oral and fecal-oral transmission models ofS. Typhimurium SL1344 infection, PECAM-1−/−mice were found to be more resistant toS. Typhimurium infection than wild-type (WT) C57BL/6 mice. While fecal shedding ofS. Typhimurium was comparable in wild-type and PECAM-1−/−mice, the PECAM-1-deficient mice had lower bacterial loads in systemic organs such as liver, spleen, and mesenteric lymph nodes than WT mice, suggesting that extraintestinal dissemination was reduced in the absence of PECAM-1. This reduced bacterial load correlated with reduced tumor necrosis factor (TNF), interleukin-6 (IL-6), and monocyte chemoattractant protein (MCP) levels in sera of PECAM-1−/−mice. Followingin vitrostimulation of macrophages with either wholeS. Typhimurium, lipopolysaccharide (LPS) (Toll-like receptor 4 [TLR4] ligand), or poly(I·C) (TLR3 ligand), production of TNF and IL-6 by PECAM-1−/−macrophages was reduced. Together, these results suggest that PECAM-1 may have multiple functions in resistance to infection withS. Typhimurium, including binding to host cells, extraintestinal spread to deeper tissues, and regulation of inflammatory cytokine production by infected macrophages.

Spike Protein of SARS-CoV-2 Activates Macrophages and Contributes to Induction of Acute Lung Inflammations in Mice

2020 ◽  
Author(s):  
Xiaoling Cao ◽  
Yan Tian ◽  
Vi Nguyen ◽  
Yuping Zhang ◽  
Chao Gao ◽  
...  
Keyword(s):  
Viral Entry ◽  
Inflammatory Responses ◽  
Host Cells ◽  
Spike Protein ◽  
Raw264.7 Cells ◽  
Inflammatory Factors ◽  
Mrna Levels ◽  
Viral Burden

Background: Coronavirus disease 2019 (COVID-19) patients exhibit multiple organ malfunctions with a primary manifestation of acute and diffuse lung injuries. The Spike protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is crucial to mediate viral entry into host cells; however, whether it can be cellularly pathogenic and contribute to pulmonary hyper-inflammations in COVID-19 is not well known. Methods and Findings: In this study, we developed a Spike protein-pseudotyped (Spp) lentivirus with the proper tropism of SARS-CoV-2 Spike protein on the surface and tracked down the fate of Spp in wild type C57BL/6J mice receiving intravenous injection of the virus. A lentivirus with vesicular stomatitis virus glycoprotein (VSV-G) was used as the control. Two hours post-infection (hpi), Spp showed more than 27-75 times more viral burden in the lungs than other organs; it also exhibited about 3-5 times more viral burden than VSV-G lentivirus in the lungs, liver, kidney and spleen. Acute pneumonia was evident in animals 24 hpi. Spp lentivirus was mainly found in LDLR+ macrophages and pneumocytes in the lungs, but not in MARC1+ macrophages. IL6, IL10, CD80 and PPAR-γ were quickly upregulated in response to infection of Spp lentivirus in the lungs in vivo as well as in macrophage-like RAW264.7 cells in vitro. We further confirmed that forced expression of the Spike protein in RAW264.7 cells could significantly increase the mRNA levels of the same panel of inflammatory factors. Conclusions: Our results demonstrate that the Spike protein of SARS-CoV-2 alone can induce cellular pathology, e.g. activating macrophages and contributing to induction of acute inflammatory responses.

scholarly journals Lactobacillus reuteri-derived extracellular vesicles maintain intestinal immune homeostasis against lipopolysaccharide-induced inflammatory responses in broilers

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Rujiu Hu ◽  
Hua Lin ◽  
Mimi Wang ◽  
Yuezhen Zhao ◽  
Haojing Liu ◽  
...  
Keyword(s):  
Gene Expression ◽  
Immune System ◽  
Extracellular Vesicles ◽  
Lactobacillus Reuteri ◽  
Inflammatory Responses ◽  
Immune Homeostasis ◽  
Tnf Α ◽  
Chicken Model

Abstract Background Lactobacillus reuteri strains are widely used as probiotics to prevent and treat inflammatory bowel disease by modulating the host’s immune system. However, the underlying mechanisms by which they communicate with the host have not been clearly understood. Bacterial extracellular vesicles (EVs) have been considered as important mediators of host-pathogen interactions, but their potential role in commensals-host crosstalk has not been widely studied. Here, we investigated the regulatory actions of EVs produced by L. reuteri BBC3, a gut-associated commensal bacterium of Black-Bone chicken, in the development of lipopolysaccharide (LPS)-induced intestinal inflammation in a chicken model using both in vivo and in vitro experiments. Results L. reuteri BBC3 produced nano-scale membrane vesicles with the size range of 60–250 nm. Biochemical and proteomic analyses showed that L. reuteri BBC3-derived EVs (LrEVs) carried DNA, RNA and several bioactive proteins previously described as mediators of other probiotics’ beneficial effects such as glucosyltransferase, serine protease and elongation factor Tu. In vivo broiler experiments showed that administration of LrEVs exerted similar effects as L. reuteri BBC3 in attenuating LPS-induced inflammation by improving growth performance, reducing mortality and decreasing intestinal injury. LrEVs suppressed the LPS-induced expression of pro-inflammatory genes (TNF-α, IL-1β, IL-6, IL-17 and IL-8), and improved the expression of anti-inflammatory genes (IL-10 and TGF-β) in the jejunum. LrEVs could be internalized by chicken macrophages. In vitro pretreatment with LrEVs reduced the gene expression of TNF-α, IL-1β and IL-6 by suppressing the NF-κB activity, and enhanced the gene expression of IL-10 and TGF-β in LPS-activated chicken macrophages. Additionally, LrEVs could inhibit Th1- and Th17-mediated inflammatory responses and enhance the immunoregulatory cells-mediated immunosuppression in splenic lymphocytes of LPS-challenged chickens through the activation of macrophages. Finally, we revealed that the reduced content of both vesicular proteins and nucleic acids attenuated the suppression of LrEVs on LPS-induced inflammatory responses in ex vivo experiments, suggesting that they are essential for the LrEVs-mediated immunoregulation. Conclusions We revealed that LrEVs participated in maintaining intestinal immune homeostasis against LPS-induced inflammatory responses in a chicken model. Our findings provide mechanistic insight into how commensal and probiotic Lactobacillus species modulate the host’s immune system in pathogens-induced inflammation.

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